Instrument to indicate air pressure and temperature



G. E. BARNHART ,270,494 INSTRUMENT TO INDICATE AIR PRESSURE AND TEMPERATURE 7 Jan. 20, 1942.

Filed Jan. 2, 1940 INVENTOR. Georqe E. Barnhori ATTORN Patented Jan. 20, 1942 INSTRUMENT too INDICATE AIR ms ssUnE AND TEMPERATURE George E. Barnhart, Pasadena, Calif.

Application January 2. 1940, Serial No. 311,999

6 Claims.

This invention relates toscientific instruments; The general object of the invention isto provide a novel instrument for determining atmospheric conditions.

Another object of the invention is to provide a novel barometer.

A further object of the invention is to provide an instrument including novel means to indicate air temperature and pressure.

Another object of the invention is to provide 'a novel heat insulated barometer.

Other objects and the advantages of this invention will be apparent from the following description taken in connection with the accompanying drawing, wherein:

Fig. 1 is a face view of my improved instrument;

Fig. 2 is an enlarged fragmentary longitudinal section through the device shown in Fig. 1;

Fig. 2A is an enlarged fragmentary sectional detail showing the inner end of the capillary tube;

Fig. 3 is an enlarged section taken on line 3--3, Fig. 2; r

Fig. 4 is a front view of a further modified form of my invention; and r Fig. 5 is an enlarged fragmentary longitudinal section through the device shown in Fig. 4.

Referring to the .drawing by reference characters I have indicated my improved instrument generally at I0. As shown the device includes an outer glass tube l2 which at the lower end merges into an elongated bulb portion l3. Within the tube I2 I provide a reduced glass capillary tube M which at the upper end flares outwardly and is fused to the outer tube l2 to form anopen topped cup-like chamber l5. The lower end of the capillary tube l4 projects into'and is fused to an enlarged elongated bulb member 15. The bulb I6 is of less length and diameter than the bulb [3. Between the bulbs 13 and I6 and between the tubes I2 and I4 I arrange suitable cushion spacers I1 and I1.

Within the capillary tube M I provide a drop of liquid l8 such as hydrochloric acid. To prevent the drop l8 from ever falling into the bulb [6 the lower end of the capillary tube is bevelled as at H! and a tapered cup member is fused thereto in such a manner as to leave a minute passageway 21 between the end of the capillary tube and the cup.

Projecting through the walls of the bulbs 13 and I6 and into the inner bulb I6 I provide a thermometer 22 with the bulb portion 23 thereof within the inner bulb 16.

The thermometer member 22 is fused to both the inner and outer bulbs.

, The tube 12 and the bulb I3 are evacuated through a neck 24 which is then closed andithe thermometer 22 the support has a neutral or zero point 28 indicated thereon and graduated indicia 29 at each side of the neutral point.

To exclude light and heat radiation from th capillary tube as much as possible the inner surface of the bulb i3 and the tube l2 are silvered-as indicated at 30 and the outer surface of the bulb l6 and the capillary tube 14 are silvered as indicated at 3.1- in Fig. 3-. .A portion of the inner surface of the outer tube I2 is left unsilvered to provide a viewing area 32 and likewise a portion of the capillary tube I4 is unsilvered to provide .a viewing area 33.

When the atmospheric pressure decreases the gas within the bulb l6 expands and forces the drop i8 upward and when the atmospheric pressure increases it forces the drop l8 down and compresses the gas within the bulb Ni.

capillary tubing 5| which adjacent the lower end extends into and is fused to an enlarged glass bulb 52. The lower end of the capillary tube 5| similar to the capillary tube I4 is bevelled as at 53 and a tapered cup member 54 is fused thereto in such a manner as to leave a minute passageway 55 between the end of the capillary tube and the cup.

Within the capillary tube 5| I provide a drop of liquid 56 such as hydrochloric acid. Surrounding uatedindicia 21 is provided on the support ateach side of the neutral point. Likewise adjacent the The thermometer indicates the temperature thermometer and includes a length of glass the capillary tube I provide an enlarged tube 51 which at the lower end is fused to the bulb 52.

The upper end of the capillary tube 5| is enlarged and fused to the outer tube 51 to form an open cup-like chamber 58 in which medical gauze or spun glass fiber is positioned to prevent foreign matter from entering the capillary tube.

The tube 5! is evacuated and gas such as nitrogen is placed in the bulb 52.

A thermometer 60 extends into and is fused to the bulb 52 with the bulb 6! of the thermometer positioned in the bulb 52.

It will be understood that if desired the enlarged tube 5'! may be omitted from the modification should such a structure be desirable for certain uses. It will be understood that gases other than nitrogen may be employed and that indicators other than hydrochloric acid may also be employed and that the indicator may be suitably colored if desired.

From the foregoing it will be apparent that I have invented a novel scientific instrument which is extremely sensitive in use and which can be readily manufactured.

Having thus described my invention, I claim:

1. In an instrument of the class described, an outer tube having an enlarged bulb at one end, an inner capillary tube disposed within said outer tube, said inner tube having a bulb disposed within and spaced from the first bulb, spacing means between said bulbs and between said tubes, the space between said tubes and bulbs being exhausted, the outer end of said capillary tube be ing flared outwardly and fused to the wall of the outer tube to form a cup-like receptacle communicating with the outer end of the capillary tube and with the atmosphere, and a drop of fluid in said capillary tube and a filling of gas in said inner bulb and tube.

2. In an instrument of the class described, an outer tube having an enlarged bulb at one end, an inner capillary tube disposed within said outer tube, said inner tube having a bulb disposed within'and spaced from the first bulb, spacing means between said bulbs and between said tubes, the space between said tubes and bulbs being exhausted, the outer end of said capillary tube beingflared outwardly and fused to the wall of the outer tube to form a cup-like receptacle communicating with the outer end of the capillary tube and with the atmosphere, porous material in'said receptacle, a drop of fluid in said capillary tube and a filling of gas in said inner bulb and tube, and a thermometer extending through the walls of said bulbs.

3. In an instrument of the class described, an outer tube having an enlarged bulb at one end, an inner capillary tube disposed within said outer tube, said inner tube having a bulb disposed within and spaced from the first bulb, spacing means between said bulbs and between said tubes, the space between said tubes and bulbs being exhausted, the outer end of said capillary tube being flared outwardly and fused to the wall of the outer tube to form a cup-like receptacle communicating with the outer end of the capillary tube and with the atmosphere, porous material in said receptacle, a drop of liquid in said capillary tube and a filling of gas in said inner bulb and tube, a thermometer tube extending through and fixed to the walls of said inner and outer bulbs, said thermometer tube having a bulb thereon and having a capillary aperture communicating with the bulb and a filling of heat responsive fluid in the thermometer tube bulb.

4. In an instrument of the class described, an outer tube having an enlarged bulb at one end, an inner capillary tube disposed within said outer tube, said inner tube having a bulb disposed within and spaced from the first bulb, spacing means between said bulbs and between said tubes, the

space between said tubes and bulbs being exhausted, the outer end of said capillary tube being fused to the wall of the outer tube to form a receptacle communicating with the outer end of the capillary tube and with the atmosphere, filtering material in said receptacle, a drop of fluid in said capillary tube and a filling of gas in said inner bulb and tube, a thermometer tube extending through and fixed to the walls of said inner and outer bulbs, said thermometer tube having a bulb thereon and having a capillary aperture communicating with the bulb and a filling of heat responsive fluid in the thermometer tube bulb. 1

5. In an instrument of the class described, an outer receptacle, a capillary tube disposed with in said receptacle, said tube having a bulb thereon, said tube communicating with the bulb the space between said receptacle and tube, being exhausted, one end of said capillary tube being open to the atmosphere, a drip cup on the inner end of said capillary tube and within the bulb, a drop of fluid in said capillary tube and a filling of gas in said bulb and tube.

6. In an instrument of the class described, an outer tube having an enlarged bulb at one end, an inner capillary tube having an end open to the atmosphere and disposed within said outer tube, said inner tube having a bulb disposed within and spaced from the first bulb, the space between said tubes and bulbs being exhausted, the. outer end of said capillary tube being secured to the wall of the outer tube, a drop of fluid in said capillary tube and a filling of gas in said inner bulb and tube.

GEORGE E. BARNI-LART. 

